This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. PRD1 is a well known bacterial virus infecting gram negative bacteria. It has an icosahedral capsid surrounding a lipid bilayer. The lipid membrane vesicle in turn encloses the viral genome.The genome is a linear dsDNA molecule of 15 kbp with covalently associated terminal proteins. The genome is packaged into the empty procapsid through a specific vertex into the lipid vesicle. PRD1 has served as a key virus in developing the theory of how viruses are assembled and how the entire virus universe in constructed. Due to its internal membrane the interest to this virus has been considerable. The availability of several mutant viruses with missing components at the specific vertex will help in the interpretation of the structural data through difference imaging. There are also several mutants affecting the entry processes and the entry phenomena may be addressed by tomographic techniques.